This invention relates to motor control systems and, more particularly, to a braking arrangement for use with a universal motor driven by an SCR phase control circuit.
There are many applications where it is desired to quickly decelerate a motor for fast stopping thereof. For example, in a sewing machine, when an operator releases the foot controller it is desirable to bring the sewing machine to a complete halt relatively quickly so that unwanted stitches are not sewn. Additionally, when a sewing machine is to be stopped with the needle in a predetermined position, such as up or down, the sewing machine must be quickly stopped when the needle reaches the desired position after the operator releases the foot controller.
It is therefore an object of this invention to provide a braking arrangement for a motor which results in quick stopping of the motor.
It is possible to quickly stop a motor by applying a mechanical brake. However, this is not entirely satisfactory due to heat buildup and wear of parts.
It is therefore another object of this invention to provide an electrical braking arrangement for a motor.
In the prior art, many electrical braking arrangements for a motor are known. For example, it is a well known technique to brake a motor by short circuiting the armature. It is also known to maintain current through the field windings when the motor armature is short circuited. Both of these techniques result in a rapid braking of the motor. However, the known implementations of these techniques have not been entirely satisfactory as for example by requiring relatively complex and expensive circuitry.
It is therefore a further object of this invention to provide an efficient circuit for rapidly braking a motor.